Photodetector and photo detecting system

ABSTRACT

There is provided a photodetector which has the function of measuring the intensity distribution of light with a simple and inexpensive construction and which has a selectivity for a measured wavelength band. The photodetector comprises a transparent semiconductor electrode part and counter electrode part on each of which a sensitizing dye is applied, and a buffer layer sandwiched therebetween, the counter electrode part or the transparent semiconductor electrode part being divided into a plurality of electrode cells. Thus, it is possible to realize a compact photodetector which carries out a photoelectric transfer using part of light in a wavelength band absorbed into the sensitizing dye and which has a wavelength selectively.

Cross Reference to Related Application

[0001] This application claims benefit of priority under 35USC §119 toJapanese Patent Application No. 2000-95804, filed on Mar. 30, 2000, thecontents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of The Invention

[0003] The present invention relates generally to a photodetector and aphoto detecting system. More specifically, the invention relates to aphotodetector and photo detecting system capable of detectinginformation about the two-dimensional intensity distribution andwavelength distribution of incident light by the improvement of atransmission photodetector.

[0004] 2. Description of Related Art

[0005] Now that optical technology is applied to various systems, lightreceiving elements serving as light detecting means are applied as keydevices in applications for all of light applied apparatuses. Theselight receiving elements are devices which are formed of a semiconductorand which generate an electromotive force by the effect of a p-njunction. The mechanism of the photoelectric transfer of a lightreceiving element will be briefly described below.

[0006] The mechanism of the photoelectric transfer is a mechanismwherein electrons and positive holes finally accumulate in an n-regionand a p-region, respectively, to cause a potential difference althoughbehavior is different in three places, i.e., in the vicinity of thesurface, in a space charge region and within a crystal. First, lightbeams absorbed into the vicinity of the surface excite a highconcentration of electrons and positive holes to cause the electrons andpositive holes to diffuse toward the interior at which theconcentrations of the electrons and positive holes are low. When theelectrons and positive holes reach the space charge region of the p-njunction, the electrons drop in accordance with the potential gradientto reach the n-region, and the positive holes are blocked by thepotential gradient to stay in the inlet of the space charge region.

[0007] Then, light beams absorbed into the p-n junction space chargeregion slightly inside of the surface produce electrons and positiveholes there, and the electrons and positive holes move in accordancewith the potential gradient to accumulate in the n-region and p-region.Finally, only the long-wavelength components of light beams reach theinterior of the crystal, and the positive holes produced in the insiden-region reach the space charge region by diffusion to be collected in ap-region by the electric field. Thus, the electromotive force isgenerated on both sides of the p-n junction when the p-n junction isirradiated with light.

[0008] Conventional light receiving elements are generally arranged atthe end of an optical path as shown in, e.g., FIG. 35, since light beamsdo not pass through the surface forming p-n junction. That is, in FIG.35, light beams which are split by a beam splitter 2 provided in anoptical path 1 are led to a light receiving element 3. Therefore, thedetecting optical system having the light receiving element 3 often hasa complicated construction. In addition, by providing the beam splitter2, it is not possible to avoid shifting the optical axis and generatingnoises on the wave front of beams to have a bad influence. Therefore,particularly in measuring systems requiring to propagate beams at a longdistance, there is a problem in that it is difficult to adapt such adetecting optical system.

[0009] On the other hand, with the advance of optical applied system inrecent years, it is increasingly requested to propagate light beams of aplurality of wavelength on the same optical axis. Conventionally,systems for dispersing light beams using a half mirror or a polarizedbeam splitter taking account of the polarized state are often used fordetecting light beams having a single wavelength such as laser beams.However, with the development of recent short-wavelength lasers, thereare many examples where lasers of a plurality of wavelengths have thesame optical axis. In an optical disc system serving as one of theexamples, two lasers having different wavelengths of 780 nm and 635 nmare used for reading a compact disc (CD) and a digital versatile disc(such as DVD) by the same system. In the current technology, detectingsystems for the two wavelengths are often separately constructed, sothat it is considered that the construction of the detecting opticalsystem is increasingly complicated with the advance of opticaltechnology.

[0010] As one of examples where incident light has a wide frequencyband, there is an image sensor. As a typical example, there is a chargecoupled device (CCD) for video camera or the like wherein natural lightis incident thereon. The image sensor for video camera is provided withan optical system having three CCDS, as shown in FIG. 36, for dividingincident light beams into three kinds of wavelength bands of RGB todetect the divided light beams, respectively. That is, in theconstruction shown in this figure, a red component is separated by aprism 5, which is arranged in an optical path 1, to be detected by a CCD4A. In addition, a green component separated by a prism 6 is detected bya CCD 4B, and a blue component separated by a prism 7 is detected by aCCD 4C. By adapting this detecting optical system, a light-intensitysignal detected after the separation into primary colors is extracted asan information signal. In order to realize a high performance imagesensor, it is required to separate incident light of such a widewavelength band into light beams of primary colors to provide detectingsystems for the respective primary colors, and it is indispensable toprovide the complicated detecting system shown in FIG. 36.

[0011] In order to simplify the above described detecting opticalsystem, a photodetector for partially transmitting light beams isproposed. As conventional photodetectors having light transmittingfunctions, there are reverse transparent electrode optical sensors whichare mainly used for a solar battery and which are provided with anamorphous silicon optical sensor on a glass substrate, and see-throughoptical sensors for allowing the transmission of light beams by forminga micropore in silicon.

[0012] However, in the reverse transparent electrode optical sensors,color is limited to the band gap of silicon. Therefore, colors otherthan red, e.g., blue and green, can not be absorbed so that thewavelength band is limited. In addition, since the see-through opticalsensors allow the micropore to transmit light beams, it is not possibleto enhance both of transmittance and conversion efficiency, and it isnot possible to adjust absorption wavelength.

[0013] In addition, as shown in FIG. 37, a transmission photodetector isrealized by producing a thin-film photodiode using a process forcontrolled-thinning a silicon substrate. That is, in the example shownin this figure, a silicon oxide mask M is utilized forcontrolled-thinning a part of a silicon substrate S by etching with TMAH(Tetra-Methyl-Ammonium-Hydroxide) (see FIG. 37(a)), a p-n junction isformed (see FIG. 37(b)), and electrodes E are formed to form a thin-filmphotodiode (see FIG. 37(c)).

[0014] However, in such a detector, there are problems in that theproduction costs are high and the light transmittance is low. Inaddition, since the spectra of wavelengths of light beams absorbed anddetected are fixed due to silicon serving as the material, there is aproblem in that the use as a photodetector is very limited.

[0015] As described above, the conventional photodetector having thelight receiving element must be arranged at the end of the optical pathsince it can not transmit light beams. Simultaneously, there areproblems in that it is indispensable to disperse light beams byproviding the beam splitter or the like in the optical path in order tolead light beams to the photodetector arranged at the end, that theconstruction of the optical system is complicated, that the optical axisis finely shifted, and that noises are generated on the wave front ofbeams.

[0016] With the advance of optical technology in recent years, ifdetecting optical systems, the number of which corresponds to the numberof used wavelengths, are provided due to the use of lasers of aplurality of wavelengths and/or the use of the frequency band which issplit to be detected, the detecting optical systems tend to beincreasingly complicated.

[0017] In addition, although there are conventionally light transmittingdetectors having limited uses, fine adjustment is difficult and theproduction costs are high, so that these detectors are not suitably usedas inexpensive and high performance photodetectors.

SUMMARY OF THE INVENTION

[0018] It is therefore an object of the present invention to eliminatethe aforementioned problems and to provide a photodetector, which isinexpensive and has a simple construction and excellent productivity,for carrying out a photo detection capable of selecting a wavelengthband.

[0019] In order to accomplish the aforementioned and other objects,according to a first aspect of the present invention, a transmissionphotodetector comprises a first transparent electrode, a secondtransparent electrode, and a photoelectric transfer part sandwichedbetween the first and second transparent electrodes, wherein at leastone of the first and second transparent electrodes is divided into aplurality of electrode cells, and the photoelectric transfer part iscommon to the plurality of electrode cells.

[0020] In this transmission photodetector, the photoelectric transferpart may comprise: a transparent semiconductor layer stacked on thefirst transparent electrode; a sensitizing dye film, stacked on thetransparent semiconductor layer, absorbing light in a wavelength bandincluding a predetermined wavelength; and a carrier transporting layersandwiched between the sensitizing dye film and the second transparentelectrode.

[0021] Alternatively, the photoelectric transfer part may comprise: atransparent semiconductor layer stacked on the first transparentelectrode; a sensitizing dye film, stacked on the transparentsemiconductor layer, absorbing light in a wavelength band including apredetermined wavelength; and a dielectric layer sandwiched between thesensitizing dye film and the second transparent electrode.

[0022] Alternatively, the photoelectric transfer part may comprise anorganic p-type semiconductor layer stacked on the first transparentelectrode, and an organic n-type semiconductor layer stacked on theorganic p-type semiconductor layer, wherein the second transparentelectrode is stacked on the organic n-type semiconductor layer.

[0023] According to a second aspect of the present invention, atransmission photodetector comprises: a first transparent electrode; atransparent semiconductor layer stacked on the first transparentelectrode; a sensitizing dye film, stacked on the transparentsemiconductor layer, absorbing light in a wavelength band including apredetermined wavelength; a second transparent electrode; and a carriertransporting layer sandwiched between the sensitizing dye film and thesecond transparent electrode, wherein at least one of the first andsecond transparent electrodes is divided into a plurality of electrodecells.

[0024] According to a third aspect of the present invention, atransmission photodetector comprises: a first transparent electrode; atransparent semiconductor layer stacked on the first transparentelectrode; a sensitizing dye film, stacked on the transparentsemiconductor layer, absorbing light in a wavelength band including apredetermined wavelength; a second transparent electrode; and adielectric layer sandwiched between the sensitizing dye film and thesecond transparent electrode, wherein at least one of the first andsecond transparent electrodes is divided into a plurality of electrodecells.

[0025] According to a fourth aspect of the present invention, atransmission photodetector comprises: a first transparent electrode; anorganic p-type semiconductor layer stacked on the first transparentelectrode; an organic n-type semiconductor layer stacked on the organicp-type semiconductor layer; and a second transparent electrode stackedon the organic n-type semiconductor layer, wherein at least one of thefirst and second transparent electrodes is divided into a plurality ofelectrode cells.

[0026] According to a fifth aspect of the present invention, a stackedtype photodetector comprises: a first transmission photodetectorconfigured to carry out a photoelectric transfer with respect to lightin a first wavelength band including a predetermined wavelength; and asecond photodetector, stacked on the first transmission photodetector,configured to detect light passing through the first transmissionphotodetector.

[0027] In this stacked type photodetector, the first transmissionphotodetector may comprise: a first transparent electrode; a transparentsemiconductor layer stacked on the first transparent electrode; asensitizing dye film stacked on the transparent semiconductor layer; asecond transparent electrode; and a carrier transporting layersandwiched between the sensitizing dye film and the second transparentelectrode.

[0028] Alternatively, the first transmission photodetector may comprise:a first transparent electrode; a transparent semiconductor layer stackedon the first transparent electrode; a sensitizing dye film stacked onthe transparent semiconductor layer; a second transparent electrode; anda dielectric layer sandwiched between the sensitizing dye film and thesecond transparent electrode.

[0029] Alternatively, the first transmission photodetector may comprise:a first transmission electrode; an organic p-type semiconductor layerstacked on the first transparent electrode; an organic n-typesemiconductor layer stacked on the organic p-type semiconductor layer;and second transparent electrode stacked on the organic n-typesemiconductor layer.

[0030] In the above described stacked type photodetector, the secondphotodetector may have a transparent electrode, at least one of thefirst or second transparent electrode of the first photodetector and thetransparent electrode of the second photodetector being divided into aplurality of electrode cells.

[0031] The second photodetector may have a third transparent electrodestacked on one principal plane of a transparent substrate, the secondtransparent electrode of the first transmission photodetector beingstacked on the other principal plane of the transparent substrate.

[0032] In this case, each of the second and third transparent electrodesmay be divided into a plurality of electrode cells, the plurality ofelectrode cells of the second transparent electrode being the samedividing patterns as those of the third transparent electrode.

[0033] The plurality of electrode cells may have substantially equalareas symmetrically with respect to a point on the optical axis ofincident light.

[0034] The second photodetector may have a fourth transparent electrodeprovided so as to face the third transparent electrode, each of thefirst and fourth transparent electrodes having a constant potentialduring operation.

[0035] The stacked type photodetector may further comprise a signalprocessor, integrally provided with the photodetector, configured toprocess circuit processing an electric signal every one of the dividedelectrode cells, the electric signal being obtained via each of thesecond and third transparent electrodes.

[0036] In the stacked type photodetector, a second wave length bandphotoelectric-transferred by the second photodetector may include alonger wavelength component than that of the first wavelength bandphotoelectric-transferred by the first transmission photodetector.

[0037] With the above described construction, according to the presentinvention, there is realized a photodetector selectively detecting apredetermined wavelength component while transmitting light. Thisphotodetector can very simply form a detecting optical system.

[0038] Since this photodetector can be produced by an inexpensive andsimple producing process, it is possible to provide a high-performanceoptical detecting system at low costs. Since this photodetector can havea wavelength selectivity, only a predetermined wavelength component canalso be detected in an optical system wherein laser beams of a pluralityof wavelengths are arranged on the same optical axis.

[0039] Such a transmission photodetector can also receive light fromboth surfaces, so that it is possible to provide a detecting opticalsystem capable of being applied to the detection of various positionshifts.

[0040] If photo detecting units for selecting a wavelength to carry outa detection are stacked, the sensitivity of detection can be improved.If the selecting wavelengths of the stacked type photo detecting unitsare set to be different from each other, it is possible to provide aphotodetector capable of simultaneously detecting light beams of aplurality of wavelengths.

[0041] One feature of the structure of this photodetector is that thephotodetector has divided electrodes. Since these electrodes are formedon both surfaces of the same transparent substrate, the dividedelectrodes can be easily aligned with each other. With such aconstruction of the stacked type photodetector, it is possible tosimplify the producing process, and it is possible to realize aninexpensive photodetector.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be understood more fully from thedetailed description given herebelow and from the accompanying drawingsof the preferred embodiments of the invention. However, the drawings arenot intended to imply limitation of the invention to a specificembodiment, but are for explanation and understanding only.

[0043] In the drawings:

[0044]FIG. 1A is a schematic sectional view showing an example of thebasic construction of a photodetector according to the presentinvention;

[0045]FIG. 1B is a conceptual drawing showing an operation model of aphotodetector according to the present invention;

[0046]FIG. 2A is a perspective view showing the appearance of the firstpreferred embodiment of a transmission photodetector according to thepresent invention;

[0047]FIG. 2B is a sectional view of the transmission photodetector inthe first preferred embodiment;

[0048]FIG. 3 is a conceptual drawing showing an applied example of atransmission photodetector according to the present invention;

[0049]FIG. 4 is a conceptual drawing showing an example wheretransmitted light passing through a photodetector 100 is also utilizedfor detecting a position shift;

[0050]FIG. 5 is a conceptual drawing showing an example of atransmission photodetector having an electrode cell divided into fourparts;

[0051]FIG. 6 is a graph showing the difference between the currentsignals of a carrier transporting substance and a dielectric;

[0052]FIG. 7 is a conceptual drawing showing a principal part of amethod for preparing a transmission photodetector according to thepresent invention;

[0053]FIG. 8 is a sectional view showing an example of a constructionwherein a counter electrode is not divided;

[0054]FIG. 9 is a conceptual drawing showing an example of aconstruction wherein an electrode cell is divided into unequal areas;

[0055]FIG. 10A is a plan view of the second preferred embodiment of atransmission photodetector according to the present invention;

[0056]FIG. 10B is a sectional view of a principal part of thetransmission photodetector in the second preferred embodiment;

[0057]FIG. 11 is a conceptual drawing showing an example where thetransmission photodetector in the second preferred embodiment isarranged in a detecting optical system for use in a video camera or thelike;

[0058]FIG. 12 is a conceptual drawing showing a construction wherein atransmission photodetector 204 is arranged at one place;

[0059]FIG. 13 is a conceptual drawing for explaining the third preferredembodiment of the present invention;

[0060]FIG. 14 is a conceptual drawing showing the construction of thefourth preferred embodiment of a transmission photodetector according tothe present invention;

[0061]FIG. 15 is a conceptual drawing showing the construction of thefourth preferred embodiment of a transmission photodetector according tothe present invention;

[0062]FIG. 16(a) is a plan view of the fifth preferred embodiment of atransmission photodetector according to the present invention, and FIG.16(b) is a sectional view of a principal part thereof;

[0063]FIG. 17(a) is a perspective view showing the appearance of thesixth preferred embodiment of a stacked type transmission photodetectoraccording to the present invention, and FIG. 17(b) is a sectional viewthereof;

[0064]FIG. 18 is a conceptual drawing showing a construction wherein atransparent electrode of a second counter electrode part is not divided;

[0065]FIG. 19 is a conceptual drawing showing a detecting opticalsystem;

[0066]FIG. 20 is a conceptual drawing a construction for detectingdifferent two kinds of wavelengths;

[0067] FIGS. 21(a) and 21(b) are plan and sectional views showing anexample of a construction wherein an electrode cell of a detector isdivided into four parts;

[0068]FIG. 22 is a conceptual drawing showing a preferred embodiment ofa double-layer stacked type transmission photodetector having anelectrode cell divided into four parts;

[0069]FIG. 23 is a process drawing showing a principal part of a methodfor preparing the sixth preferred embodiment of a stacked typetransmission photodetector 600 according to the present invention;

[0070]FIG. 24(a) is a plan view showing the appearance of the sixthpreferred embodiment of a stacked type transmission photodetector 700according to the present invention, and FIG. 24(b) is a sectional viewof a principal part thereof;

[0071]FIG. 25 is a conceptual drawing a preferred embodiment wherein acolor image is read;

[0072]FIG. 26(a) is a plane view showing the appearance of the eighthpreferred embodiment of a stacked type transmission photodetectoraccording to the present invention, and FIG. 26(b) is a sectional viewof a principal part thereof;

[0073]FIG. 27 is a conceptual drawing showing a construction wherein acolor image is divided into RGB to form electronic images;

[0074]FIG. 28 is a conceptual drawing an example of an optical system;

[0075]FIG. 29 is a conceptual drawing showing a photodetector whereinthree transmission photo detecting units are aligned;

[0076]FIG. 30 is a conceptual drawing showing the construction of theninth preferred embodiment of the present invention;

[0077]FIG. 31 is a conceptual drawing showing the construction of thetenth preferred embodiment of the present invention;

[0078]FIG. 32 is a conceptual drawing showing the construction of theeleventh preferred embodiment of the present invention;

[0079]FIG. 33 is a conceptual drawing showing a detection system of anoptical disc system;

[0080]FIG. 34 is a conceptual drawing showing the construction of thetwelfth preferred embodiment of the present invention;

[0081]FIG. 35 is a conceptual drawing showing a construction wherein adetector is arranged at the end of an optical path;

[0082]FIG. 36 is a conceptual drawing showing an optical system havingthree CCDS; and

[0083]FIG. 37 is a sectional view showing a process for producing athin-film photodiode using a process for controlled-thinning a siliconsubstrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0084] Referring now to the accompanying drawings, the preferredembodiments of the present invention will be described below in detail.

First Preferred Embodiment: Transmission Photodetector With ElectrodeDivided Into Four Parts

[0085]FIG. 1A is a schematic sectional view showing an example of abasic construction of a preferred embodiment of a photodetectoraccording to the present invention. That is, a photodetector 1001comprises a first electrode part 1004 formed on a transparent substrate1002, a second electrode part which is formed on a transparent substrate1003 and which comprises two divided first and second electrode cells1006 and 1007, and a photoelectric transfer part 1005 sandwiched betweenboth electrode parts.

[0086] Light beams entering the transparent substrate 1002 pass throughthe transparent substrate 1002 and the first electrode part 1004 tocause the movement of electrons and positive holes in the photoelectrictransfer part 1005. As a result, the electromotive force due to themovement of electrons and positive holes in the vicinity of the firstelectrode cell 1006 of the divided second electrode part is generatedbetween the first electrode part 1004 and the first electrode cell 1006,and the electromotive force in the vicinity of the other secondelectrode cell 1007 is generated between the first electrode part 1004and the second electrode cell 1007.

[0087] Thus, by dividing the second electrode part into two or moreelectrode cells, the electromotive forces depending on the intensitiesof light beams entering the regions divided by a dividing line can beseparately extracted.

[0088] In conventional divided type photodetectors, portionscorresponding to the photoelectric transfer part 1005 and firstelectrode part 1004 of the photodetector according to the presentinvention are also divided, so that it is difficult to detect lightbeams entering an intermediate region between the divided regions. Inthe photodetector divided into two parts as shown in FIG. 1A as anexample, the area of the intermediate region is very small, whereas in aphotodetector divided into a large number of regions, the components ofthe electromotive force which should be generated in the intermediateregions are large to consequently cause the lowering of thephotoelectric transfer efficiency.

[0089] On the other hand, according to the present invention, there isprovided an efficient photodetector which can also carry out thephotoelectric transfer with respect to the intermediate regions betweenthe divided regions. In addition, it is possible to provide aphotodetector wherein a portion to be divided may be only the secondtransparent electrode part and which can be easily formed by patterningor the like.

[0090] With the above described construction, the operation of atransmission photodetector in this preferred embodiment will bedescribed below.

[0091]FIG. 1B is a conceptual drawing showing an operation model of aphotodetector according to the present invention. Light beams entering atransmission photodetector 100 reach a dye sensitizing transparentsemiconductor electrode part 60 via a transparent substrate 14. Lightbeams in the absorption wavelength region of a sensitizing dye film 17are herein absorbed to excite the sensitizing dye film 17. By thisexcitation, positive holes are generated at the highest occupiedmolecular orbital (HOMO) level of the sensitizing dye film, andelectrons are generated at the lowest unoccupied molecular orbital(LUMO) of the sensitizing dye film to move to a transparentsemiconductor layer 16 of titanium oxide (TiO₂) or the like.

[0092] Furthermore, as an energy level required to operate the abovedescribed photodetector, the LUMO level of each of the sensitizing dyefilm is preferably higher than the conductive band level of thetransparent semiconductor layer by 0.5 eV or less.

[0093] In a buffer layer 65 of an oxidation-reduction electrolyte whichis a carrier transporting substance, positive holes generated at theHOMO level of the sensitizing dye film 17 move to the buffer layer 65,and positive holes move to a counter electrode part 12 through thebuffer layer 65 to enter the counter electrode. On the other hand,electrons reaching the transparent semiconductor layer 16 move to atransparent electrode 15. The electrons in this transparent electrodemove to a wire 67, and positive holes in the counter electrode 12 move awire 68, so that the transmission photodetector according to the presentinvention is operated by the current flowing through the wires 67 and68.

[0094]FIGS. 2A and 2B show the appearance of the first preferredembodiment of a transmission photodetector according to the presentinvention. FIG. 2A is a perspective view of the appearance thereof, andFIG. 2B is a sectional view thereof.

[0095] This photodetector 100 is a transmission photodetector forselectively absorbing light beams having a predetermined wavelength bandto carry out a photoelectric transfer. This transmission photodetectorcomprises a dye sensitizing transparent semiconductor electrode part 11,a counter electrode part 12, and a buffer layer 13 sandwiched betweenboth electrode parts. The dye sensitizing transparent semiconductorelectrode part 11 comprises a transparent electrode 15 and transparentsemiconductor layer 16 which are formed on a transparent substrate 14,and a sensitizing dye film 17 absorbed into the semiconductor layer 16.

[0096] The counter electrode part 12 comprises a transparent electrodeformed on a transparent substrate 50. As shown in the figure, thistransparent electrode is divided into four cells 18, 19, 20 and 21 whichare electrically isolated from each other, and wires 22, 23, 24 and 25are arranged so as to be able to separately extract current signalswhich are generated in the respective electrode cells.

[0097] While the counter electrode part 12 has been divided into thefour cells having equal areas in the example shown in FIGS. 2A and 2B,the electrode part 12 may be divided into a plurality of linear cells ora large number of cells in the form of a matrix. The respectivetransparent electrodes and electrode parts are divided symmetricallywith respect to a point on the center of the optical axis of incidentlight.

[0098] When the photodetector is applied to a power monitor fordetecting the quantity of incident light, it is not required to dividethe electrode part.

[0099] Also with respect to the electrode cells 18, 19, 20 and 21 shownin FIGS. 2A and 2B, the principle of operation is the same. On the basisof this principle of operation, a current flows through the wiringcorresponding to each of the cells in proportion to the quantity oflight, with which each of the cells is irradiated. In order to obtainhigh quality signals, the potential level of the transparent electrode15 should be the ground level. In this case, positive potentials aregenerated in the plurality of counter electrode cells to detect avoltage corresponding to each of the cells by the current-voltageconversion. That is, the wire 26 of the transparent electrode 15 isgrounded.

[0100] An applied example of the transmission photodetector 100 with theabove described construction will be described below.

[0101]FIG. 3 is a conceptual drawing showing an applied example of atransmission photodetector according to the present invention.

[0102] If the transmission photodetector 100 in this preferredembodiment is arranged in an optical path 1 as shown in this figure, asimple detecting optical system can be formed. By the detecting opticalsystem shown in this figure, the outputs of divided electrode cells 18,19, 20 and 21 can be compared with each other to calculate the quantityof position shift of the photodetector from a reference beam or thequantity of position shift of the optical axis from the photodetector.

[0103] Light beams passing through the transmission photodetector can beutilized for another use.

[0104]FIG. 4 is a conceptual drawing showing an example wheretransmitted light passing through photodetectors 101 and 103 are alsoutilized for detecting a position shift. By using the plurality oftransmission photodetectors 101 and 103 according to the presentinvention as shown in this figure, it is possible to form a detectingoptical system for detecting a position shift between a plurality ofmoving structural bodies on the basis of a reference beam 71.

[0105] In this case, the distance between the structural bodies 102 and104 may be 1 m or more. When light beams of a plurality of wavelengthbands are incident on then optical axis shown in FIG. 4, thetransmission photodetectors 101 and 103 provided for the respectivestructural bodies may be produced by using sensitizing dyes of differentcompositions. In this case, the position shift of a first structuralbody with respect to a light beam of a first wavelength band is detectedby a first photodetector, and the position shift of a second structuralbody with respect to a light beam of a second wavelength band.

[0106] In the preferred embodiment shown in FIGS. 3 and 4, the positionshift of the optical axis of incident light from the center of thephotodetector can be two-dimensionally detected by detecting the outputsignals of the four divided electrode cells 18, 19, 20 and 21 as thequantities of incident light on the corresponding cells and by carryingout a comparison operation, specifically an addition/subtractionoperation. When signals obtained by the respective electrode cells arethus used for carrying out a signal processing, a signal processingcircuit is preferably provided so as to be very close to thephotodetector in order to detect and process a very weak current with ahigh S/N.

[0107]FIG. 5 is a conceptual drawing showing an example of atransmission photodetector having four divided electrode cells. In thisfigure, signals of electrode cells 81, 82, 83 and 84 detected by atransmission photodetector 105 are inputted to a signal processingcircuit 89 via wires 85, 86, 87 and 88. In this signal processingcircuit 89, the addition and subtraction with respect to the respectivesignals are carried out. For example, if signals inputted from the wires85 and 86 are added to be subtracted from the sum of signals inputtedfrom the wires 87 and 88, the quantity of position shift of the opticalaxis of incident light in X directions can be detected. Similarly, thequantity of position shift in Y directions can also be detected by anaddition/subtraction operation, so that the shift of the optical axes intwo directions of X and Y axes can be detected. This quantity ofposition shift has the same meaning as that of the quantity of positionshift of the photodetector with respect to the reference beam.

[0108] With respect to the transmission photodetector shown in FIG. 1B,the carrier transporting substance of the oxidation-reductionelectrolyte has been used as the buffer layer 65. In this case, acurrent flows between the electrodes while light beams are incidentthereon, and no current flows while no light beams are incident thereon.

[0109] On the other hand, the buffer layer 65 may be formed of adielectric. In this case, the principle of operation of thephotodetector is slightly different, and detected signals have differentcharacteristics with respect to incident light.

[0110]FIG. 6 is a graph showing this difference in current signal.

[0111] When the buffer layer is formed of a carrier transportingsubstance, a current signal shown in FIG. 6(b) flows with respect toincident light signal shown in FIG. 6(a).

[0112] On the other hand, when the buffer layer is formed of adielectric, an electric field is generated in a transmission opticalsensor unit by the above described movement of charges, so that adisplacement current flows through a wire. By the function of thisdisplacement current, positive charges are generated in the transparentelectrode, and negative charges are generated in the counter electrode.At this time, the transmission photodetector according to the presentinvention is operated by detecting the displacement current flowingbetween the wires.

[0113] That is, since the displacement current flows as a timedifferentiated value of the quantity of incident light, a positive pulseis generated between the electrodes as shown in FIG. 6(c) simultaneouslywith the incidence of light shown in FIG. 6(a). In addition, no currentflows during irradiation with light, and a negative pulse current flowssimultaneously with the disappearance of light.

[0114] The speed of response of the photodetector will be describedbelow. That is, the light absorption of the sensitizing dye film 17 ineach of the transmission photo detecting units and the electrontransition to the transparent semiconductor layer 16 occur infemtoseconds, and electrons transferred to the transparent semiconductorlayer 16 return to the sensitizing dye film 17 in nanoseconds. If thecarrier transporting substance is used as the buffer layer 65, themovement of positive holes from the sensitizing dye film 17 to thecarrier transporting substance 65 occurs to fill the HOMO level of thesensitizing dye film 17 with positive holes, in picoseconds after themovement of electrons from the sensitizing dye film 17 to thetransparent semiconductor film 16. Therefore, the return of electronsfrom the transparent semiconductor layer 16 to the sensitizing dye film17 is difficult to occurs since the return of electrons occurs innanoseconds which is slower than the movement of the movement ofpositive holes.

[0115] The speed of response of the transmission photo detecting unit isdetermined by a speed at which the positive holes moved from thesensitizing dye film 17 diffuse in the carrier transporting substance65. For example, if an electrolyte utilizing ion diffusion is used asthe carrier transporting substance 65, the ion diffusion rate is usuallyslow, so that the unit is difficult to response to signals in MHz.

[0116] If a dielectric, not a carrier transporting substance, is used asthe buffer layer 65, positive holes at the HOMO level of the sensitizingdye film 17 produced by light absorption do not move, so that themovement of electrons from the transparent semiconductor layer 16 occursin nanoseconds. Therefore, the speed of response of the unit is higherthan that when the carrier transporting substance is used, so that it ispossible to response to signals in tens MHz.

[0117] The respective members of the transmission photodetectoraccording to the present invention will be described below.

[0118] The transparent electrode 11 for use in the present inventionmeans a construction wherein the transparent electrode 15 of atransparent conductive layer is provided on the surface of thetransparent substrate 14.

[0119] The transparent substance 14 may be formed of any one transparentplate materials, e.g., a glass or a polymer film.

[0120] The transparent electrode 15 may be formed of any one oftransparent materials having conductivity on the surface of theelectrode. For example, the transparent electrode 15 is preferablyformed of tin oxide doped with fluorine, indium or aluminum, or zincoxide. A very small amount of a non-transparent electrode layer, such asplatinum, gold, silver, copper or aluminum, may be included if it doesnot so obstruct the transmission of light. The transparent electrode 15may be divided into a plurality of patterns on the transparentsubstrate. In this case, wires are mounted so as to extract signals fromthe respective cells to the outside of the cell, respectively.

[0121] The auxiliary electrode (wire) is preferably formed of anon-transparent metal, such as platinum, gold, silver, copper oraluminum, or a material having a high conductivity, such as graphite.

[0122] The transparent semiconductor layer 16 is preferably formed of asemiconductor which absorbs a small quantity of light in a visible lightregion. As preferred metal oxide semiconductors, there are oxides oftransition metals, such as oxides of titanium, zirconium, hafnium,strontium, zinc, indium, yttrium, lanthanum, vanadium, niobium,tantalum, chromium, molybdenum and tungsten, combined oxides thereof,and mixtures of the oxides. Specifically, there are perovskites, such asSrTiO₃, CaTiO₃, BaTiO₃, MgTiO₃and SrNb₂O₆, combined oxides thereof, andmixture of the oxides, such as GaN.

[0123] The absorption of the sensitizing dye layer 17 onto the surfaceof the transparent semiconductor layer 16 does not occur so thatthickness of the absorbed sensitizing dye layer 17 exceeds the thicknessof one molecular layer to a few molecular layers. In order to controlthe apparent shade of color of elements, fine irregularities can beformed on the surface of the transparent semiconductor layer 16 as shownin FIG. 1B to control the effective surface area. In order to form astructure of irregularities, a fine grain structure may be used. Forexample, when a sintered body of fine particles of TiO₂ having a grainsize of 10 nm is used for preparing a fine structure, the effectivesurface area can be controlled by adjusting the thickness of the finegrain layer. The structure of irregularities is preferably formed sothat the whole specific surface area is in the range of from 100 to1000.

[0124] The transparent electrode and transparent semiconductor layerhave properties for transmitting light beams of a wavelength region ofvisible light, and transmit at least 30%, preferably 50%, morepreferably 70% or more, of light beams having a wavelength of 300 nm to800 nm.

[0125] The sensitizing dye layer 17 absorbs incident light to be in anexcited state. Thereafter, the sensitizing dye layer 17 transferselectrons to the transparent semiconductor layer, and then, receiveselectrons from a solid carrier transporting substance. Therefore, theLUMO level of the sensitizing dye film 17 must be equal to or higherthan the conductive band level of the transparent semiconductor layer16. In order to cause the sensitizing dye film 17 to be stronglyabsorbed onto the surface of the transparent semiconductor layer 16, thesensitizing dye film 17 preferably has a functional group, such ascarboxyl group, hydroxyalkyl group, hydroxyl group, sulfonic group orcarboxyalkyl group, in its molecule.

[0126] The sensitizing dye film 17 preferably has a structure which hasthe above described functional group in any one of ruthenium-tris,ruthenium-bis, osmium-tris and osmium-bis type transition metalcomplexes, multinuclear complexes, ruthenium-cis-diaqua-bipyridylcomplexes, phthalocyanine dyes, porphyrin dyes, perylene dyes,anthraquinone dyes, azo dyes, quinophthalone dyes, naphthoquinone dyes,cyanine dyes and merocyanine dye. In order to obtain a desired color, amixture of these dyes may be used.

[0127] As the dielectric material forming the buffer layer 65, any oneof crystalline or amorphous organic molecules may be used. Thecrystalline organic molecules include various kinds of metalphthalocyanines, perylene tetracarboxylic acid, polynuclear aromaticcompounds such as perylene and coronene, tetrathiafulvalene,charge-transfer complexes such as tetracyanoquinodimethane, amorphousmaterials such as Alq3, diamines, various kinds of oxadiazoles,conductive macromolecules such as polypyrroles, polyanilines,poly-N-vinylcarbazoles and polyphenylene-vinylenes.

[0128] As the carrier transporting substance forming the buffer layer65, any one of ion transport materials and electron/hole transportmaterials may be used. The ion transport materials include salts, suchas iodine ion containing salts, sulfonimide salts, alkylimidazoliumsalts, tetracyanoquinodimethane salts and dicyanoquinodiimine salts. Theion transport materials are preferably liquid ion transport materialswhich are selected from acetonitrile, ethylene carbonate, propylenecarbonate and mixtures thereof, and gel ion transport materials whichare formed by mixing any one of host polymers, such as polyethyleneoxides, polyacrylonitriles, polyvinylidene fluorides, polyvinylalcohols, polyacrylic acids and polyacrylic amides, in any one of theabove described liquid ion transport materials to polymerize themixture.

[0129] At the electron/hole transport materials, crystalline oramorphous organic molecules may be used. The crystalline organicmolecules include polynuclear aromatic compounds such as perylene andcoronene, various kinds of metal phthalocyanines, perylenetetracarboxylic acid, tetrathiafulvalene, charge-transfer complexes suchas tetracyanoquinodimethane, amorphous materials, aluminumquinodimethane, diamines, oxadiazoles, polypyrroles, polyanilines,poly-N-vinylcarbazoles and polyphenylene-vinylenes.

[0130] The ion transport material used in this preferred embodiment isan acetonitrile/ethylene carbonate mixture solvent electrolyte solutioncomprising about 0.5 mol/l of tetrapropylammonium iodine, about 0.02mol/l of potassium iodine, and 0.03 mol/l of iodine.

[0131] If the photodetector in this preferred embodiment comprises theabove described members, the thickness of the transparent substrate canbe thinned to be about 0.1 mm, and the thickness of other elements isnegligible, so that the whole thickness can be about 0.5 mm.

[0132] The point of a method for preparing a transmission photodetectoraccording to the present invention will be described below.

[0133]FIG. 7 is a conceptual drawing showing a principal part of anexample of a method for preparing a transmission photodetector accordingto the present invention.

[0134] First, a method for producing a TiO₂ film serving as thetransparent semiconductor layer 16 is as follows. About 2 mol/l of TiCl₄is dissolved in ethanol, and methanol is added thereto to obtain atitanium alkoxide containing about 50 mg/ml titanium. After the titaniumalkoxide thus obtained is hydrolyzed, the hydrolyzed titanium alkoxideis applied on a first transparent electrode, on which platinum has beendeposited as an auxiliary electrode (see FIG. 7(a)), to be sintered atabout 400° C. for about 30 minutes to obtain a TiO₂ film serving as atransparent semiconductor (see FIG. 7(b)). At this time, the TiO₂ filmpreferably has a specific surface area of about 600 when irregularitiesare provided with respect to a case where the surface has been flat, anda thickness of about 5 μm.

[0135] Then, a sensitizing dye film 17 is absorbed onto the transparentsemiconductor layer 16 thus formed (see FIG. 7(c)). At this step, theobtained TiO₂ film is immersed in a sensitizing dye containing ethanolsolution. After it is immersed therein, the TiO₂ film is taken out to bewashed with ethanol. In this preferred embodiment, the dye sensitizingtransparent semiconductor electrode part is produced by the abovedescribed method.

[0136] The counter electrode part 12 is formed by patterning atransparent electrode on a transparent substrate (see FIGS. 7(d) and7(e)).

[0137] The respective parts thus prepared are bonded and stacked via aspacer serving as a frame of the buffer layer (see FIG. 7(f), and acarrier transporting substance or a dielectric is injected via a void ofthe spacer to complete assembly (see FIG. 7(g)).

[0138] In the example shown in FIGS. 2A and 2B, the counter electrodepart 12 is divided, and the transparent electrode part 11 having thetransparent semiconductor absorbing the sensitizing dye is not divided.However, the transparent electrode part 11 may be divided withoutdividing the other counter electrode part 12.

[0139]FIG. 8 is a sectional view showing an example of a constructionwherein a counter electrode is not divided.

[0140] In the example shown in FIG. 5, the electrode cells are separatedso as to have substantially equal areas, the electrode cells may beseparated so as to have unequal areas.

[0141]FIG. 9 is a conceptual drawing showing an example of aconstruction wherein electrode cells are separated so as to have unequalareas. That is, in this construction, electrode cells C1 through C6 areseparated so as to have unequal areas.

Second Preferred Embodiment: Transmission Photodetector With DividedElectrode: Motion Vector Estimator: One-dimensional Scanner

[0142] The second preferred embodiment of the present invention will bedescribed below.

[0143]FIGS. 10A and 10B show the appearance of the second preferredembodiment of a transmission photodetector 200 according to the presentinvention. FIG. 10A is a plan view thereof, and FIG. 10B is a sectionalview of a principal part thereof.

[0144] The photodetector shown in the figures has a construction whereina counter electrode surface 12 of the transmission photodetectordescribed as the first preferred embodiment is divided into a pluralityof cells C1, C2, . . . which have an equal area.

[0145]FIG. 11 shows an example where the transmission photodetector inthis preferred embodiment is arranged in a detecting optical system foruse in a video camera or the like. In the case of the use in thispreferred embodiment, the matrix of the electrode cells has a largescale of 600×480 or the like.

[0146] A typical image sensor for a video camera is provided with anoptical system shown in FIG. 11, which has three CCDs in order toseparate incident light beams into three kinds of wavelength bands ofRGB to detect them, respectively. In FIG. 11, a red component isseparated by a prism 206, which is arranged in an optical path 205, tobe detected by a CCD 209. In addition, a green component separated by aprism 207 is detected by a CCD 210, and a blue component separated by aprism 208 is detected by a CCD 211. By adapting this detecting opticalsystem, light intensity signals separated into three colors to bedetected can be extracted as information signals.

[0147] If transmission photodetectors 201, 202 and 203 in this preferredembodiment are arranged as shown in FIG. 11, part of picture signalsinputted to the respective CCDs can be used for estimating a “motionvector” of an image. This motion vector is used for compensating the“movement” of picture signals, i.e., a so-called “movement of thehands”, which is caused by the influence of the vibration of a person,who picks up an image, on a video camera, and for grasping picturesignals, which move on a CCD sensor at a predetermined frequency, as amoving direction and a moving distance. After this motion vector isestimated, if it is determined that there is a hand movement component,the picture signals are corrected in accordance with the motion vectorto record signals as picture signals from which the influence of themovement of the hands has been removed.

[0148] In fact, the detecting optical system is constructed as shown inFIG. 11, and the differentiated value, i.e., the time variation, ofpicture signals detected in the respective electrode cells Cn (n=1, 2, .. . ) in the preferred embodiment shown in FIGS. 10A and 10B isobtained, so that the motion vector can be estimated. Furthermore, inthe transmission photodetector 200 in this preferred embodiment, if thebuffer layer 65 is formed of a carrier transporting substance, anadditional differentiating circuit is required, whereas if the bufferlayer 65 is formed of a dielectric, the differentiated signal of aninputted light signal can be extracted as a signal output as shown inFIG. 6. That is, if the buffer layer 65 is formed of a dielectric, thedifferentiated value of a signal can be immediately obtained byutilizing it in the use requiring a differentiating circuit.

[0149] While three transmission photodetectors have been arranged in theconstruction of FIG. 11, a single transmission photodetector 204 may bearranged as shown in FIG. 12. In this case, if the sensitizing dye filmof the transmission photodetector 204 is set so as to absorb wavelengthcomponents which do not interfere with RGB components of picturesignals, it is possible to carry out a motion vector estimation withoutdeteriorating the quality of the original picture signals.

[0150] When the electrode cells having a large matrix structure areadopted as shown in FIGS. 10A and 10B as an example, the sequentialsignal reading system is often used for detecting signals in therespective cells. In brief, in this system, condensers are provided soas to correspond to the respective electrode cells, so that therespective electrode cells are previously charged at a specific voltage.This voltage is periodically and sequentially charged for each of thecells. If discharge occurs for some reason, a voltage required forcharge can be extracted as a signal. When a pulse current flows throughone of the electrode cells of the photodetector, if the circuit isconstructed so that a corresponding one of the condensers discharges inaccordance with the current value, the value of the pulse signal can bedetected as a charged value when an additional charge is periodicallycarried out.

Third Preferred Embodiment: Input Unit Arranged Directly On Screen

[0151] The third preferred embodiment of the present invention will bedescribed below.

[0152]FIG. 13 is a conceptual drawing for explaining the third preferredembodiment of the present invention. That is, in this preferredembodiment, the transmission photodetector 200 in the second preferredembodiment is arranged on an original screen 301 to acquire imageinformation of the original screen. In this preferred embodiment,external light reflecting on the original surface 301 to return isdetected by the transmission photodetector 200, so that the imageinformation of the original surface can be received.

[0153] The original surface 301 may be image signals on anelectronically projected display, or image information drawn on a paper.

[0154] By means of a pen-like input terminal 302 capable of outputtinglight beams of wavelengths, which can be detected by the transmissionphotodetector 200 according to the present invention, i.e., laser beamsof a predetermined wavelength, it is possible to write on thephotodetector to input information. In this case, image informationhaving originally existed on the original surface 301 has been detectedfrom the reverse of the transmission photodetector 200, so thatinformation inputted by the input terminal 302 can be electronicallyaligned with the originally existing image information to be inputted.

Fourth Preferred Embodiment: Actuator With Sensor

[0155]FIGS. 14 and 15 are conceptual drawings showing the constructionof the fourth preferred embodiment of a transmission photodetectoraccording to the present invention. In this transmission photodetector400, the thickness of the transparent substrate 14 of the transparentelectrode part 11 of the transmission photodetector 100 shown in FIGS.2A and 2B is increased, and a mirror surface 441 is provided. In thetransmission photodetector 400 with this construction, incident lightbeams 442 reflect on the mirror surface 441 to be reflected light beams443, with which the four divided electrode cells of the counterelectrode part 12 are irradiated twice. As shown in these figures as anexample, when the incident light beams 442 are obliquely incident on themirror surface 441, the inclined angle can be detected by comparingsignals, which are detected by the respective electrode cells, by meansof an arithmetic circuit 446.

[0156] In addition, if the detected signal current is used as it is orafter passing through an amplifier circuit, to be inputted to a drivingmeans 448 for driving the transparent photodetector as shown in FIG. 15,the mirror surface 441 of the transmission photodetector 400 can berotated to be adjusted so as to correct the detected inclined angle.

[0157] That is, there is realized a system having the function ofcorrecting the angle on the basis of the signal detected by thetransmission photodetector 400. The driving means 448 may be any one ofdriving systems, such as electromagnetic, piezoelectric andelectrostatic driving systems. However, when the detected current valueis used as it is, the current value detected by the photodetector isvery small, so that it is considered that the electrostatic drivingsystem is suitably used.

[0158] While the correction has been carried out by the rotation in thispreferred embodiment, a servo mechanism may be provided so that theoutput of the arithmetic circuit has a predetermined value by paralleltranslations or other motions.

[0159] While the object to be driven has been the transmissionphotodetector itself in this preferred embodiment, it may be anotherobject (not shown), such as the power of a light source for supplyinglight which is incident on the transmission photodetector.

Fifth Preferred Embodiment: Alignment/Incident Light From Both Surface

[0160] The fifth preferred embodiment of the present invention will bedescribed below.

[0161]FIG. 16(a) is a plan view of a transmission photodetector in thispreferred embodiment, and FIG. 16(b) is a sectional view of a principalpart thereof.

[0162] This preferred embodiment is suitable for case where a member 501having a minute hole 502 is irradiated with incident light 503 toprecisely align the center of the optical axis of incident light withthe center of the hole 502. In the alignment procedure, a reference beam504 is first given from the reverse of the member 501 having the hole,and while the light beam passing through the hole is detected by thefour divided electrode cells C1 through C4, the transmissionphotodetector 500 is aligned with the member 501 to be fixed thereto byan adhesive or the like.

[0163] Thereafter, the transmission photodetector 500 is irradiated withincident light 503, and while the incident light 503 is detected by thefour divided electrode cells C1 through C4, the optical axis is aligned.Thus, the transmission photodetector according to the present inventioncan detect irradiation light on both surfaces, so that the shownadjusting procedure can be carried out.

[0164] The transmission photodetectors having the plurality of dividedelectrodes have been described above in the first through fifthpreferred embodiment of the present invention.

[0165] As the sixth through twelfth preferred embodiments of the presentinvention, transmission photodetectors having a plurality of stackedcells will be described below.

Sixth Preferred Embodiment: Double-Layer Photodetector With DividedElectrodes

[0166] First, the sixth preferred embodiment of the present invention ofthe present invention will be described below.

[0167]FIG. 17(a) is a perspective view showing the appearance of thesixth preferred embodiment of a stacked transmission photodetectoraccording to the present invention, and FIG. 17(b) is a sectional viewthereof.

[0168] This photodetector 600 comprises a first transmission photodetecting unit 10 for selectively absorbing a light beams of a firstwavelength band to carry out a photoelectric transfer, and a secondtransmission photo detecting unit 30 for selectively absorbing a lightbeam of a second wavelength band to carry out a photoelectric transfer,the first transmission photo detecting unit 10 being stacked on thesecond transmission photo detecting unit 30 via a transparent substrate50 of an insulator.

[0169] The first transmission photo detecting unit 10 comprises a firstdye sensitizing transparent semiconductor electrode part 11, a firstcounter electrode part 12, and a first buffer layer 13 which issandwiched between both electrode parts. The first dye sensitizingtransparent semiconductor electrode part 11 comprises a transparentelectrode 15 and transparent semiconductor layer 16 which are formed ona transparent substrate 23, and a sensitizing dye film 17 which isabsorbed onto the semiconductor layer 16.

[0170] Similarly, the second transmission photo detecting unit 30comprises a second dye sensitizing transparent semiconductor electrodepart 31, a second counter electrode part 32, and a second buffer layer33 which is sandwiched between both electrode parts. The second counterelectrode part 32 is formed on the reverse surface of the firsttransparent electrode part 12 via the transparent substrate 50. Similarto the first dye sensitizing transparent semiconductor electrode part,the second dye sensitizing transparent semiconductor electrode part 31comprises a transparent electrode 35 and transparent semiconductor layer36 which are formed on a transparent substrate, and a sensitizing dyefilm 37 which is absorbed onto the semiconductor layer 36.

[0171] The first counter electrode part 12 comprises a transparentelectrode part which is formed on the transparent substrate 50. As shownin the figure, this transparent electrode is divided into two cells 18and 19 which are electrically isolated from each other, and wires 20 and21 are arranged so as to be able to separately extract current signalswhich are generated in the respective electrode cells.

[0172] On the other hand, the second counter electrode part provided onthe reverse surface of the transparent substrate 50 is divided intocells 38 and 39, each of which has the same shape as that of each of thedivided cells of the first transparent electrode. The cells 18 and 19are aligned with the cells 38 and 39 via the transparent substrate 50,respectively. Also in the second transparent electrode, wires 40 and 41are arranged so as to be able to separately extract current signalswhich are generated in the respective electrode cells.

[0173] The wire 22 of the first transparent electrode and the wire 42 ofthe second transparent electrode are connected to each other to begrounded.

[0174] While each of the counter electrode parts has been divided intothe two cells in the example shown in FIG. 17, it may be divided into aplurality of linear cells, or a plurality of cells in the form of amatrix. The respective transparent electrodes and electrode parts aresymmetrically divided with respect to on a point or line the center ofthe optical axis of incident light.

[0175] At least one of the first and second counter electrode parts maybe divided. As shown in FIG. 18 as an example, only the first counterelectrode part may be divided into electrode cells 18 and 19 withoutdividing the transparent electrode 45 of the second counter electrodepart.

[0176] The basic operation of the transparent photo detecting units 10and 30 constituting the stacked type transmission photodetector in thispreferred embodiment with the above described construction is the sameas that described referring to FIG. 1B, so that the detaileddescriptions thereof are omitted.

[0177] In the stacked type transmission photodetector shown in FIG. 17as an example, light beams, which have not been absorbed by the firsttransmission photo detecting unit 10, pass through the transparentsubstrate 50 to be incident on the second transmission photo detectingunit 30. Also in this case, a current corresponding to the quantity oflight, with which the respective cells are irradiated, can be similarlydetected by the pattern of the divided cells of the transparentelectrode provided on the counter electrode part 32.

[0178] In the stacked type transmission photodetector 600 with the abovedescribed construction, the first sensitizing dye film and the secondsensitizing dye film may have the same composition, or differentcompositions.

[0179] When the sensitizing dye films having the same composition areused, a detecting optical system for detecting the shift of the axis ofincident light 1 in view of the outputs of the divided electrode cellscan be formed by the detecting optical system having the constructionshown in FIG. 19 as an example. In this case, light beams of awavelength detected by the sensitizing dye films are detected by thefirst and second photo detecting units 10 and 20, so that it is possibleto increase the detection sensitivity.

[0180] On the other hand, when the first and second sensitizing dyefilms have different compositions, a first wavelength band detected bythe first transmission photodetector can be different from a secondwavelength band detected by the second transmission photodetector. Apreferred embodiment of a transmission photodetector for detectingdifferent wavelength bands according to the present invention will bedescribed below.

[0181]FIG. 20 is a conceptual drawing showing a construction fordetecting two kinds of different wavelengths. In the construction shownin this figure, a stacked type transmission photodetector 600 accordingto the present invention is provided in an optical path for light beamsin a wavelength band having a wide band width, or in an optical path inwhich light beams having a plurality of wavelengths are mixed. The firsttransmission photo detecting unit can use light beams having a firstwavelength band to carry out a photoelectric transfer to detect currentscorresponding to the respective cells, and simultaneously, use lightbeams having a second wavelength band to carry out a photoelectrictransfer to similarly detect current corresponding to the respectivecells.

[0182] For example, when two laser beams 1A and 1B of differentwavelengths are incident on the stacked type transmission photodetector600 according to the present invention, the difference between theoutput current values of the two divided electrode cells of the firsttransmission photo detecting unit 10 is derived to grasp the position ofthe optical axis of one laser beam 1A belonging to the first waveformband, and then, the difference between the output current values of thetwo divided electrode cells of the second transmission photo detectingunit 30 is derived to calculate the position of the optical axis of theother laser beam 1B belonging to the second wavelength band, so that itis possible to detect the quantity of one-dimensional shift between bothof the optical axes.

[0183] In this case, the stacked type transmission photodetector 600 maybe provided in the optical paths 1A and 1B, and light beams passingthrough the photodetector 600 can be applied to another use. Inaddition, the quantity of position shift can be very simply andinexpensively detected. Moreover, if the photodetector has four dividedelectrode cells, the quantity of two-dimensional shift can be detected.

[0184] FIGS. 21(a) and 21(b) are plan and sectional views showing anexample of a construction wherein each of photodetectors has fourdivided electrode cells.

[0185] When signals thus obtained in the respective electrode cells 81,82, 83 and 84 are used for carrying out a signal processing, a signalprocessing circuit is preferably provided so as to be very close to thephotodetector in order to detect and process a very weak current with ahigh S/N.

[0186]FIG. 22 is a conceptual drawing showing a preferred embodiment ofa double-layer stacked type transmission photodetector having fourdivided electrode cells according to the present invention. That is, thesignals of the respective electrode cells 81, 82, 83 and 84, which aredetected by the first transmission photodetector 10, are inputted to asignal processing circuit 89 via wires 85, 86, 87 and 88. The respectivesignals of the second transmission photodetector 30 are similarlyinputted to the signal processing circuit 89 via a signal path (notshown), so that operations such as addition and subtraction with respectto the respective signals are carried out.

[0187] In the stacked type transmission photodetector described in thispreferred embodiment, the carrier transporting substance has been usedas the buffer layer 65. In this case, a current flows between theelectrodes while light beams are incident, and no current flows while nolight beams are incident. As described above in the first preferredembodiment, also in this preferred embodiment, the buffer layer 65 maybe formed of a dielectric. As described above referring to FIG. 6, ifthe dielectric is used, the speed of response of the unit can be higherthan that when the carrier transporting substance is used, so that it ispossible to response to signals in tens MHz.

[0188] The materials of the respective members of the stacked typetransmission photodetector in this preferred embodiment, i.e., thematerials of transparent substrates 23, 24 and 50, transparentelectrodes 15, 18, 19, 35, 38 and 39, auxiliary electrodes, transparentsemiconductors 16 and 36, sensitizing dye films 17 and 37 and dielectricmaterials, and a method for producing the same may be the same as thosein the first preferred embodiment. Therefore, the detailed descriptionsthereof are omitted.

[0189]FIG. 23 is a process drawing showing a principal part of a methodfor preparing the stacked type transmission photodetector 600 in thispreferred embodiment.

[0190] First, two transparent substrates 23 and 43 are prepared, and aTiO₂ film serving as a transparent semiconductor is applied on thesurface of each of the substrates (see FIGS. 23(a) and 23(b)), to besintered (see FIGS. 23(c) and 23(d)). Then, a sensitizing dye isabsorbed thereon (see FIGS. 23(e) and 23(f)). The details of these stepshave been described above referring to FIGS. 7(a) through 7(c).

[0191] In parallel to these steps, an intermediate transparent substrate50 is prepared (see FIG. 23(g)), and transparent electrodes arepatterned on both surfaces thereof (see FIG. 23(h)).

[0192] The respective parts thus prepared are bonded and stacked via aspacer serving as a frame of the buffer layer as shown in FIG. 23(i),and a carrier transporting substance or a dielectric is injected via avoid of the spacer to complete assembly (see FIG. 23(j)).

[0193] According to this preferred embodiment, divided transparentelectrode patterns are formed on both surfaces of the intermediatetransparent substrate 50. Therefore, it is not required to carry out acomplicated step of separately forming detecting units 10 and 30 tosubsequently align the axes of both of the divided patterns with eachother.

Seventh Preferred Embodiment: Triple-Layer Stacked Type PhotodetectorWith Divided Electrodes: One-dimensional Image Sensor: Scanner

[0194] The seventh preferred embodiment of the present invention will bedescribed below.

[0195]FIG. 24(a) is a plan view showing the appearance of the seventhpreferred embodiment of a stacked type transmission photodetector 700according to the present invention, and FIG. 24(b) is a sectional viewof a principal part thereof.

[0196] In the photodetector in this preferred embodiment, an additionallayer of a third transmission photo detecting unit is stacked on thedouble-layer stacked type transmission photodetector 600 in the sixthpreferred embodiment.

[0197] That is, a first transmission photo detecting unit 110 forresponding to light beams of a first wavelength band to carry out aphotoelectric transfer is provided nearest to the plane of incident onwhich light is incident, and subsequently, a second transmission photodetecting unit 130 for carrying out a photoelectric transfer withrespect to light beams of a second wavelength band is provided via atransparent substrate 150. The constructions of the first and secondtransmission photo detecting units are the same as those in the sixthpreferred embodiment, so that the descriptions thereof are omitted.

[0198] In this preferred embodiment, a third transmission photodetecting unit 170 is constructed so that a third dye sensitizingtransparent semiconductor electrode part is formed on the reversesurface of a transparent substrate 143 on which a dye sensitizingtransparent semiconductor electrode part 131 of a second transparentphoto detecting unit 130 is provided. That is, the third dye sensitizingtransparent semiconductor electrode part comprises a transparentelectrode 175 and transparent semiconductor layer 176 which are formedon the reverse surface of the transparent substrate 143 of the seconddye sensitizing transparent semiconductor electrode part 131, and asensitizing dye film 177 which is absorbed onto the semiconductor layer176. The third transmission photo detecting unit 170 comprises a thirdcounter electrode part 172 on the opposite surface to the third dyesensitizing transparent semiconductor electrode part, and a third bufferlayer 173 which is sandwiched between both of the electrodes.

[0199] In this preferred embodiment, each of the transparent electrodesof the counter electrode parts is divided into, e.g., about 480 cells,and the respective transmission photo detecting units are stacked sothat the cells of one of the transmission photo detecting unit arealigned with the cells of the other transmission photo detecting unit.The divided electrode cells of the first transmission photo detectingunit 110 and the divided electrode cells of the second transmissionphoto detecting unit 130 are formed on the same substrate 150 similar tothe sixth preferred embodiment, so that the alignment can be easilycarried out during the formation of the electrodes.

[0200] On the other hand, the divided electrode cells of the thirdtransmission photo detecting unit are aligned during assembly. Forexample, the same alignment mark is previously formed on the transparentsubstrates 150 and 190, and the adjustment is carried out on the basisof this mark during assembly.

[0201] In the triple-layer transmission photodetector 700 in thispreferred embodiment, the wavelength bands of light beams detected bythe three stacked photo detecting units are suitably formed so that thefirst wavelength band includes the shortest wavelength and the secondand third wavelength bands include longer wavelengths in that order,since light beams of a longer wavelength has a large momentum to have apower so as to reach the inside of the photodetector. That is, lightbeams of the short wavelength band may be detected by the photodetectornearest to the plane of incidence.

[0202] The stacked type transmission photodetector 700 thus realized canbe used for simply separating a color image into RGB to form anelectronic image.

[0203]FIG. 25 is a conceptual drawing showing a preferred embodimentwherein a color image is read out.

[0204] This triple-layer transmission photodetector is set so that thesensitizing dye film of the first transmission photo detecting unit 110absorbs blue components, the sensitizing dye film of the secondtransmission photo detecting unit 130 absorbs green components and thesensitizing dye film of the third transmission photo detecting unit 170mainly absorbs red components. This setting may be the separation intothree colors such as yellow (Y), magenta (M) and cyanogen (C) if shortwavelength components and long wavelength components are separated so asto be first and third, respectively.

[0205] The operation of a reading system shown in FIG. 25 will bedescribed below. A detecting optical system comprises a lamp 203, a lens204 and a stacked type transmission photodetector, and is mounted on amovable body 202. An original surface 201 is irradiated with light beamsemitted from the lamp, and only the linear return light beams arecondensed on the stacked type transmission photodetector. By moving themovable body in parallel to the original surface, information on theoriginal surface is sequentially collected by the photodetector. At thistime, light beams reflected on the original surface include colorinformation on the original surface to be incident on the stacked typetransmission photodetector.

[0206] The incident light beams are first inputted to the firsttransmission photo detecting unit 110 of the stacked type transmissionphotodetector. At a place at which a photoelectric transfer is carriedout by light beams absorbed into the first sensitizing dye film, apotential is generated in a corresponding divided electrode so that acurrent flows.

[0207] If an electrolyte is used as the buffer layer 65, a currentcontinues to flow while light beams of the first wavelength band areabsorbed. If the current-to-voltage conversion of this current iscarried out, it can be extracted as voltage information.

[0208] On the other hand, if a dielectric is used as the buffer layer65, a positive pulse current starts to flow simultaneously with theincidence of light beams of the corresponding first wavelength band onthe first sensitizing dye film, and a negative pulse current flows whenit is stopped. In this case, by a technique for detecting the generationof positive or negative pulse signals by means of a shift registercircuit or a flip-flop circuit, it is possible to extract intensityinformation on light having a specific wavelength included in incidentlight. A concrete technique for use in an image sensor or the like willbe briefly described. Condensers are provided so as to correspond to therespective electrode cells, so that the respective electrode cells arepreviously charged at a specific voltage. This voltage is periodicallyand sequentially charged. If discharge occurs for some reason, a voltagerequired for charge can be extracted as a signal. When a pulse currentflows through one of the electrode cells of the photodetector, if thecircuit is constructed so that a corresponding one of the condensersdischarges in accordance with the current value, the value of the pulsesignal can be detected as a discharged value when charge is periodicallycarried out.

[0209] As described above, the line irradiated with the lamp 203 isconverted into color information and intensity information by means ofthe triple-layer stacked transmission photodetector in this preferredembodiment. While the movable body moves in parallel to the original,information on each of the cells is read out in synchronism therewith,so that information on the whole original can be read out.

Eighth Preferred Embodiment: Two-dimensional Image Sensor

[0210]FIG. 26(a) is a plan view showing the appearance of the eighthpreferred embodiment of a stacked type transmission photodetectoraccording to the present invention, and FIG. 26(b) is a sectional viewof a principal part thereof.

[0211] The stacked type transmission photodetector in this preferredembodiment has a cell structure wherein the transparent electrode of thecounter electrode part of the triple-layer stacked type transmissionphotodetector 700 in the seventh preferred embodiment istwo-dimensionally symmetrically divided with respect to a point on thecenter of the optical axis of incident light. If this preferredembodiment is used as an image sensor, the matrix of the divided cellshas a large scale of 600×480 or like.

[0212] The triple-layer stacked transmission photodetector in thispreferred embodiment has the same construction as that in the seventhpreferred embodiment, except for the dividing form of the electrode, sothat the detailed descriptions thereof are omitted.

[0213] The triple-layer stacked transmission photodetector 800 formed asshown in FIG. 26 as an example can be used for simply separating a colorimage into RGB to form an electronic image.

[0214]FIG. 27 shows the appearance thereof, and FIG. 28 shows an exampleof an optical system thereof.

[0215] That is, as shown in FIG. 28, the triple-layer stacked typetransmission photodetector 800 in this preferred embodiment is arrangedat the condensed position of condensing lenses 291 and 293. That is, thetriple-layer stacked transmission photodetector in this preferredembodiment serves to be substituted for the three CCD detectors of theconventional video camera shown in FIG. 36, with a simple construction.Light beams including image information picked up as an object arecondensed at the position of the photodetector 800 by means of thecondensing lenses 291 and 292 to be detected as light intensity signalscorresponding to the respective wavelength bands of blue, green and redby means of first, second and third transmission photo detecting units210, 230 and 270, respectively. The plane distribution of these lightintensity signals can be extracted as voltage values by means of thedivided electrode cells, and the light intensity signals are inputted toa signal processing circuit to be processed as light intensitydistribution signals corresponding to the respective wavelengths.

[0216] Although the above described construction is a typicalconstruction in video cameras and so forth, it may be applied to otheroptical applied devices which have the same function.

[0217] If it is more inexpensive to separately produce the respectivetransmission photo detecting units, each of the transmission photodetecting units may have a triple-layer stacked structure as shown inFIG. 29 as an example. That is, in FIG. 29, the photodetector 900comprises three transmission photo detecting units 110, 130 and 170which are aligned after being previously produced.

Ninth Preferred Embodiment: Input Unit Arranged Directly On Screen

[0218] The ninth preferred embodiment of the present invention will bedescribed below.

[0219]FIG. 30 is a conceptual drawing showing the construction of thispreferred embodiment. FIG. 30(a) is a front view thereof, and FIG. 30(b)is a plan view thereof. That is, in this preferred embodiment, thetriple-layer stacked transmission photodetector 800 according to thepresent invention is arranged on an original screen 301 to acquire imageinformation on the original screen. However, the whole size and the sizeof each of pixels in the photodetector 800 for use in this preferredembodiment are different from those in the eighth preferred embodiment.That is, in this preferred embodiment, the photodetector 800 is formedso as to have a size corresponding to the size of the original to beincorporated.

[0220] The construction and operation in this preferred embodiment aresubstantially the same as those in the third preferred embodiment. Thatis, with the construction shown in FIG. 30, external light reflecting onthe original surface 301 to return can be used for receiving informationon the original surface to detect the information by means of thephotodetector 300. In this case, if information on the original is colorinformation, the triple-layer stacked transmission photodetector can beused as the photodetector to separately extract RGB information assignals.

[0221] The original surface may be image signals on an electronicallyprojected display, or image information drawn on a paper.

[0222] By means of a pen-like input terminal 302 capable of outputtinglight beams of a specific wavelength, e.g., laser beams, it is possibleto optionally write on the stacked type transmission photodetectoraccording to the present invention to input information. In this case,although the transmission photodetector has a single layer, if atriple-layer stacked transmission photodetector is used, colors inputtedby a pen can be separately distinguished by the wavelength of emittedlaser beams.

Tenth Preferred Embodiment: Wavelength Measuring Apparatus

[0223] The tenth preferred embodiment of the present invention will bedescribed below.

[0224]FIG. 31 is a conceptual drawing showing the construction of thispreferred embodiment. That is, also in this preferred embodiment, astacked type transmission photodetector 304 is used. This stacked typetransmission photodetector 304 may have a structure wherein a pluralityof transmission photo detecting units are stacked. FIG. 31 shows anexample where three units 310, 330 and 370 are stacked. It is not alwaysrequired to divide the electrodes of each of the transmission photodetecting units. The basic construction and operation of each of thetransmission photo detecting units are the same as those in the abovedescribed preferred embodiments, so that the descriptions thereof areomitted.

[0225] In this preferred embodiment, incident light 303 is decomposedinto three kinds of wavelength components by means of the stacked typetransmission photodetector 304. In this case, if the signal outputsdetected by the first transmission photo detecting unit 310, the secondtransmission photo detecting unit 330 and the third transmission photodetecting unit 370 are compared, it is possible to detect the ratios ofthe wavelength band components absorbed into the sensitizing dyescorresponding to the respective units. Thus, the spectra of the incidentlight 303 can be analyzed.

Eleventh Preferred Embodiment: Photodetector For Optical Disk Drive

[0226] The eleventh preferred embodiment of the present invention willbe described below.

[0227]FIG. 32 is a conceptual drawing showing the construction of thispreferred embodiment. That is, this preferred embodiment is used in anoptical applied device using light beams of a plurality of wavelengths,such as an optical disk reading system. In the shown embodiment, atransmission photodetector 400 is arranged on a typical photodetector401 which does not transmit light, so that the photodetector 400 isformed as a stacked type photodetector 410.

[0228] With this construction, light in a wavelength band which can notbe detected using only the conventional photodetector 401, particularlylight of a short wavelength, can be detected by the transmissionphotodetector 400. The divided cells of the electrodes may be divided inaccordance with the same pattern as or a different pattern from that ofthe photodetector. In this preferred embodiment, the electrode cells402, 403, 404, 405, 406 and 407 are divided in accordance with the samepattern as that of the photodetector 401 as shown in the figure. Forexample, these electrode cells are adjusted so as to carry out aphotoelectric transfer particularly in a wavelength band of about 400nm.

[0229] The stacked type photodetector 410 is designed to detect signalswith a simple detecting optical system with respect to laser beams of aplurality of wavelengths in the optical disc drive shown in FIG. 33 asan example. That is, laser beams emitted from a multi-wavelength laser411 pass through a collimator lens 412, a prism 413 and a polarizingplate 414 to be condensed on the information recording surface of anoptical disc 416 by means of an objective lens 415. At this time, partof laser beams are dispersed by the prism 413 to be condensed on a powermonitor 418 by means of a lens 417 to control the power of the laser. Onthe other hand, light beams reflected on the information recordingsurface return to the prism 413 to enter a lens 419 to be incident onthe photodetector 410 by means of a hologram element 420 or the like.The photodetector 410 detects signals for controlling the position of aspot which is condensed on the optical disc.

Twelfth Preferred Embodiment: Chromatic Aberration Recorder/Detector

[0230] The twelfth preferred embodiment of the present invention will bedescribed below.

[0231]FIG. 34 is a conceptual drawing showing the construction of thispreferred embodiment. That is, as shown in this figure, the stacked typetransmission photodetector 700 in the seventh preferred embodiment isarranged on the bottom face of a prism 430. With this construction, thechromatic aberration of incident light 1 can be detected in accordancewith wavelength spectra, so that information on the incident light canbe extracted.

[0232] While the present invention has been disclosed in terms of thepreferred embodiment, the present invention should not be limited to thepreferred embodiments.

[0233] For example, the structures and materials of the photodetectorsin the above described preferred embodiments, and the constructions,arrangements and operations of the optical systems, peripheral circuitsand driving systems in the applied examples thereof can be suitablyselected from well known structures and so forth by persons skilled inthe art to obtain the same advantages.

[0234] As described above, according to the present invention, it ispossible to provide a transmission photodetector for transmitting lightfrom both sides of its light receiving surface and for detecting light,so that it is possible to realize a compact detecting optical system byarranging the photodetector in an optical path.

[0235] In addition, according to the present invention, it is possibleto provide an efficient photodetector capable of carrying out aphotoelectric transfer also with respect to an intermediate regionbetween divided regions. It is also possible to provide a photodetectorwherein a portion to be divided may be only a second transparentelectrode part and which can be easily formed by patterning or the like.

[0236] Moreover, it is possible to easily and surely carry out thedetection of positions and the alignment of axes by suitably dividingthe transparent electrode pattern.

[0237] It is also possible to easily and surely carry out the input ofimages, the pick-up of color images, the analysis of wavelengths bystacking the transmission photodetectors.

What is claimed is:
 1. A transmission photodetector comprising a firsttransparent electrode, a second transparent electrode, at least one ofthe first and second transparent electrodes being divided into aplurality of electrode cells, and a photoelectric transfer partsandwiched between the first and second transparent electrodes, thephotoelectric transfer part being common to the plurality of electrodecells.
 2. The transmission photodetector according to claim 1 , whereinthe photoelectric transfer part comprises: a transparent semiconductorlayer stacked on the first transparent electrode; a sensitizing dyefilm, stacked on the transparent semiconductor layer, absorbing light ina wavelength band including a predetermined wavelength; and a carriertransporting layer sandwiched between the sensitizing dye film and thesecond transparent electrode.
 3. The transmission photodetectoraccording to claim 1 , wherein the photoelectric transfer partcomprises: a transparent semiconductor layer stacked on the firsttransparent electrode; a sensitizing dye film, stacked on thetransparent semiconductor layer, absorbing light in a wavelength bandincluding a predetermined wavelength; and a dielectric layer sandwichedbetween the sensitizing dye film and the second transparent electrode.4. The transmission photodetector according to claim 1 , wherein thephotoelectric transfer part comprises an organic p-type semiconductorlayer stacked on the first transparent electrode, and an organic n-typesemiconductor layer stacked on the organic p-type semiconductor layer,wherein the second transparent electrode is staked on the organic n-typesemiconductor layer.
 5. A transmission photodetector comprising: a firsttransparent electrode; a transparent semiconductor layer stacked on thefirst transparent electrode; a sensitizing dye film, stacked on thetransparent semiconductor layer, absorbing light in a wavelength bandincluding a predetermined wavelength; a second transparent electrode;and a carrier transporting layer sandwiched between the sensitizing dyefilm and the second transparent electrode; wherein at least one of thefirst and second transparent electrodes is divided into a plurality ofelectrode cells.
 6. A transmission photodetector comprising: a firsttransparent electrode; a transparent semiconductor layer stacked on thefirst transparent electrode; a sensitizing dye film, stacked on thetransparent semiconductor layer, absorbing light in a wavelength bandincluding a predetermined wavelength; a second transparent electrode;and a dielectric layer sandwiched between the sensitizing dye film andthe second transparent electrode; wherein at least one of the first andsecond transparent electrodes is divided into a plurality of electrodecells.
 7. A transmission photodetector comprising: a first transparentelectrode; an organic p-type semiconductor layer stacked on the firsttransparent electrode; an organic n-type semiconductor layer stacked onthe organic p-type semiconductor layer; and a second transparentelectrode stacked on the organic n-type semiconductor layer; wherein atleast one of the first and second transparent electrodes is divided intoa plurality of electrode cells.
 8. A stacked type photodetectorcomprising: a first transmission photodetector configured to carry out aphotoelectric transfer with respect to light in a first wavelength bandincluding a predetermined wavelength; and a second photodetector,stacked on the first transmission photodetector, configured to detectlight passing through the first transmission photodetector.
 9. Thestacked type photodetector according to claim 8 , wherein the firsttransmission photodetector comprises: a first transparent electrode; atransparent semiconductor layer stacked on the first transparentelectrode; a sensitizing dye film stacked on the transparentsemiconductor layer; a second transparent electrode; and a carriertransporting layer sandwiched between the sensitizing dye film and thesecond transparent electrode.
 10. The stacked type photodetectoraccording to claim 8 , wherein the first transmission photodetectorcomprises: a first transparent electrode; a transparent semiconductorlayer stacked on the first transparent electrode; a sensitizing dye filmstacked on the transparent semiconductor layer; a second transparentelectrode; and a dielectric layer sandwiched between the sensitizing dyefilm and the second transparent electrode.
 11. The stacked typephotodetector according to claim 8 , wherein the first transmissionphotodetector comprises: a first transmission electrode; an organicp-type semiconductor layer stacked on the first transparent electrode;an organic n-type semiconductor layer stacked on the organic p-typesemiconductor layer; and a second transparent electrode stacked on theorganic n-type semiconductor layer.
 12. The stacked type photodetectoraccording to claim 8 , wherein the second photodetector has atransparent electrode, and at least one of the first or secondtransparent electrode of the first photodetector and the transparentelectrode of the second photodetector is divided into a plurality ofelectrode cells.
 13. The stacked type photodetector according to claim 9, wherein the second photodetector has a transparent electrode, and atleast one of the first or second transparent electrode of the firstphotodetector and the transparent electrode of the second photodetectoris divided into a plurality of electrode cells.
 14. The stacked typephotodetector according to claim 10 , wherein the second photodetectorhas a transparent electrode, and at least one of the first or secondtransparent electrode of the first photodetector and the transparentelectrode of the second photodetector is divided into a plurality ofelectrode cells.
 15. The stacked type photodetector according to claim11 , wherein the second photodetector has a transparent electrode, andat least one of the first or second transparent electrode of the firstphotodetector and the transparent electrode of the second photodetectoris divided into a plurality of electrode cells.
 16. The stacked typephotodetector according to claim 8 , further comprising a transparentsubstrate including two principal planes faced each other, wherein thefirst transmission photodetector comprises a first and a secondtransparent electrodes, the second transparent electrode being stackedon one principal plane of the transparent substrate, the secondphotodetector has a third transparent electrode stacked on the otherprincipal plane of the transparent substrate.
 17. The stacked typephotodetector according to claim 16 , wherein each of the second andthird transparent electrodes is divided into a plurality of electrodecells, the plurality of electrode cells of the second transparentelectrode being the same dividing pattern as those of the thirdtransparent electrode.
 18. The stacked type photodetector according toclaim 12 , wherein the plurality of electrode cells have substantiallyequal areas symmetrically with respect to a point on the optical axis ofincident light.
 19. The stacked type photodetector according to claim 17, wherein the plurality of electrode cells have substantially equalareas symmetrically with respect to a point on the optical axis ofincident light.
 20. The stacked type photodetector according to claim 16, wherein the second photodetector has a fourth transparent electrodeprovided so as to face the third transparent electrode, and each of thefirst and fourth transparent electrodes has a constant potential duringoperation.
 21. The stacked type photodetector according to claim 16 ,further comprising a signal processor, integrally provided with thephotodetector, configured to process an electric signal every one of thedivided electrode cells, the electric signal being obtained via each ofthe second and third transparent electrodes.
 22. The stacked typephotodetector according to claim 8 , wherein a second wavelength bandphotoelectric-transferred by the second photodetector includes a longerwavelength component than that of the first wavelength bandphotoelectric-transferred by the first transmission photodetector. 23.The stacked type photodetector according to claim 9 , wherein a secondwavelength band photoelectric-transferred by the second photodetectorincludes a longer wavelength component than that of the first wavelengthband photoelectric-transferred by the first transmission photodetector.24. The stacked type photodetector according to claim 10 , wherein asecond wavelength band photoelectric-transferred by the secondphotodetector includes a longer wavelength component than that of thefirst wavelength band photoelectric-transferred by the firsttransmission photodetector.
 25. The stacked type photodetector accordingto claim 11 , wherein a second wavelength band photoelectric-transferredby the second photodetector includes a longer wavelength component thanthat of the first wavelength band photoelectric-transferred by the firsttransmission photodetector.